diffraction: two-slit experiment

Figure 5: (A) Monochromatic light incident on a pair of slits gives interference fringes (alternate light and dark bands) on a screen, (B) variation in the intensity of the light at the screen when both slits are open. With a single slit, there is no interference pattern; the intensity variation is shown by the broken line. As with Figure 4B, the same diagram would give the variation in the intensity of electrons in the corresponding electron experiment.